A suspended particle light valve window consists of a thin cell whose walls consist of glass or plastic sheets coated on their inner surfaces with transparent, electrically conducting films, and which is filled with a suspended particle fluid. The suspended particles within the fluid medium are responsive to the application of an electric field and change the optical properties of the fluid depending on the intensity and polarity of the applied electric field. Such light valves must be electrically excited by applying ac voltage, preferably squarewave, to the two conducting films. Because of their construction, the light valves are electrically capacitive in nature.
Driving them with a conventional power supply is very inefficient because the capacitance must be repeatedly charged, discharged, and recharged with opposite polarity. This can be a serious disadvantage for low-power battery operation. Higher efficiency could be achieved by connecting an inductor to the cell, and operating the cell in a resonant circuit at the drive frequency. However, the waveform in this case would be sinusoidal, not square.
It is an object of this invention to introduce a voltage drive means and method for powering capacitive suspended particle light valve windows or other capacitive circuits or cells, and which requires low power level and produces an efficient squarewave voltage cycle.
It is a further object of this invention to utilize an LC circuit to efficiently deliver a square wave voltage signal across a capacitive suspended particle light valve window or other capacitive circuit or cell using a low power dc primary voltage source.